/*
 * ParameterFactory.java July 2006
 *
 * Copyright (C) 2006, Niall Gallagher <niallg@users.sf.net>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

package wx.xml.simpleframework.xml.core;

import java.lang.annotation.Annotation;
import java.lang.reflect.Constructor;

import wx.xml.simpleframework.xml.Attribute;
import wx.xml.simpleframework.xml.Element;
import wx.xml.simpleframework.xml.ElementArray;
import wx.xml.simpleframework.xml.ElementList;
import wx.xml.simpleframework.xml.ElementListUnion;
import wx.xml.simpleframework.xml.ElementMap;
import wx.xml.simpleframework.xml.ElementMapUnion;
import wx.xml.simpleframework.xml.ElementUnion;
import wx.xml.simpleframework.xml.Text;
import wx.xml.simpleframework.xml.stream.Format;

/**
 * The <code>ParameterFactory</code> object is used to create instances
 * of the <code>Parameter</code> object. Each parameter created can be
 * used to validate against the annotated fields and methods to ensure
 * that the annotations are compatible.
 * <p>
 * The <code>Parameter</code> objects created by this are selected
 * using the XML annotation type. If the annotation type is not known
 * the factory will throw an exception, otherwise a parameter instance
 * is created that will expose the properties of the annotation.
 *
 * @author Niall Gallagher
 */
class ParameterFactory {

    /**
     * This format contains the style which is used to create names.
     */
    private final Format format;

    /**
     * Constructor for the <code>ParameterFactory</code> object. This
     * factory is used for creating parameters within a constructor.
     * Parameters can be annotated in the same way as methods or
     * fields, this object is used to create such parameters.
     *
     * @param support this contains various support functions
     */
    public ParameterFactory(Support support) {
        this.format = support.getFormat();
    }

    /**
     * Creates a <code>Parameter</code> using the provided constructor
     * and the XML annotation. The parameter produced contains all
     * information related to the constructor parameter. It knows the
     * name of the XML entity, as well as the type.
     *
     * @param factory this is the constructor the parameter exists in
     * @param label   represents the XML annotation for the contact
     * @param index   the index of the parameter in the constructor
     * @return returns the parameter instantiated for the field
     */
    public Parameter getInstance(Constructor factory, Annotation label, int index) throws Exception {
        return getInstance(factory, label, null, index);
    }

    /**
     * Creates a <code>Parameter</code> using the provided constructor
     * and the XML annotation. The parameter produced contains all
     * information related to the constructor parameter. It knows the
     * name of the XML entity, as well as the type.
     *
     * @param factory this is the constructor the parameter exists in
     * @param label   represents the XML annotation for the contact
     * @param entry   this is the entry annotation for the parameter
     * @param index   the index of the parameter in the constructor
     * @return returns the parameter instantiated for the field
     */
    public Parameter getInstance(Constructor factory, Annotation label, Annotation entry, int index) throws Exception {
        Constructor builder = getConstructor(label);

        if (entry != null) {
            return (Parameter) builder.newInstance(factory, label, entry, format, index);
        }
        return (Parameter) builder.newInstance(factory, label, format, index);
    }

    /**
     * Creates a constructor that is used to instantiate the parameter
     * used to represent the specified annotation. The constructor
     * created by this method takes three arguments, a constructor,
     * an annotation, and the parameter index.
     *
     * @param label the XML annotation representing the label
     * @return returns a constructor for instantiating the parameter
     * @throws Exception thrown if the annotation is not supported
     */
    private Constructor getConstructor(Annotation label) throws Exception {
        ParameterBuilder builder = getBuilder(label);
        Constructor      factory = builder.getConstructor();

        if (!factory.isAccessible()) {
            factory.setAccessible(true);
        }
        return factory;
    }

    /**
     * Creates an entry that is used to select the constructor for the
     * parameter. Each parameter must implement a constructor that takes
     * a constructor, and annotation, and the index of the parameter. If
     * the annotation is not know this method throws an exception.
     *
     * @param label the XML annotation used to create the parameter
     * @return this returns the entry used to create a constructor
     */
    private ParameterBuilder getBuilder(Annotation label) throws Exception {
        if (label instanceof Element) {
            return new ParameterBuilder(ElementParameter.class, Element.class);
        }
        if (label instanceof ElementList) {
            return new ParameterBuilder(ElementListParameter.class, ElementList.class);
        }
        if (label instanceof ElementArray) {
            return new ParameterBuilder(ElementArrayParameter.class, ElementArray.class);
        }
        if (label instanceof ElementMapUnion) {
            return new ParameterBuilder(ElementMapUnionParameter.class, ElementMapUnion.class, ElementMap.class);
        }
        if (label instanceof ElementListUnion) {
            return new ParameterBuilder(ElementListUnionParameter.class, ElementListUnion.class, ElementList.class);
        }
        if (label instanceof ElementUnion) {
            return new ParameterBuilder(ElementUnionParameter.class, ElementUnion.class, Element.class);
        }
        if (label instanceof ElementMap) {
            return new ParameterBuilder(ElementMapParameter.class, ElementMap.class);
        }
        if (label instanceof Attribute) {
            return new ParameterBuilder(AttributeParameter.class, Attribute.class);
        }
        if (label instanceof Text) {
            return new ParameterBuilder(TextParameter.class, Text.class);
        }
        throw new PersistenceException(label, "Annotation %s not supported", label);
    }

    /**
     * The <code>ParameterBuilder<code> is used to create a constructor
     * that can be used to instantiate the correct parameter for the
     * XML annotation specified. The constructor requires three
     * arguments, the constructor, the annotation, and the index.
     *
     * @see java.lang.reflect.Constructor
     */
    private static class ParameterBuilder {

        /**
         * This is the entry that is used to create the parameter.
         */
        private final Class entry;

        /**
         * This is the XML annotation type within the constructor.
         */
        private final Class label;

        /**
         * This is the parameter type that is to be instantiated.
         */
        private final Class type;

        /**
         * Constructor for the <code>PameterBuilder</code> object. This
         * pairs the parameter type with the annotation argument used
         * within the constructor. This allows constructor to be selected.
         *
         * @param type  this is the parameter type to be instantiated
         * @param label the type that is used within the constructor
         */
        public ParameterBuilder(Class type, Class label) {
            this(type, label, null);
        }

        /**
         * Constructor for the <code>PameterBuilder</code> object. This
         * pairs the parameter type with the annotation argument used
         * within the constructor. This allows constructor to be selected.
         *
         * @param type  this is the parameter type to be instantiated
         * @param label the type that is used within the constructor
         * @param entry this is the entry used to create the parameter
         */
        public ParameterBuilder(Class type, Class label, Class entry) {
            this.label = label;
            this.entry = entry;
            this.type = type;
        }

        /**
         * Creates the constructor used to instantiate the label for
         * the XML annotation. The constructor returned will take two
         * arguments, a contact and the XML annotation type.
         *
         * @return returns the constructor for the label object
         */
        public Constructor getConstructor() throws Exception {
            if (entry != null) {
                return getConstructor(label, entry);
            }
            return getConstructor(label);
        }

        /**
         * Creates the constructor used to instantiate the parameter
         * for the XML annotation. The constructor returned will take
         * two arguments, a contact and the XML annotation type.
         *
         * @param label the type that is used within the constructor
         * @return returns the constructor for the parameter object
         */
        public Constructor getConstructor(Class label) throws Exception {
            return getConstructor(Constructor.class, label, Format.class, int.class);
        }

        /**
         * Creates the constructor used to instantiate the parameter
         * for the XML annotation. The constructor returned will take
         * two arguments, a contact and the XML annotation type.
         *
         * @param label the type that is used within the constructor
         * @param entry this is the entry used to create the parameter
         * @return returns the constructor for the parameter object
         */
        public Constructor getConstructor(Class label, Class entry) throws Exception {
            return getConstructor(Constructor.class, label, entry, Format.class, int.class);
        }

        /**
         * Creates the constructor used to instantiate the parameter
         * for the XML annotation. The constructor returned will take
         * three arguments, a constructor, an annotation and a type.
         *
         * @param types these are the arguments for the constructor
         * @return returns the constructor for the parameter object
         */
        private Constructor getConstructor(Class... types) throws Exception {
            return type.getConstructor(types);
        }
    }
}
